In cooperation with the California Birth Defects Monitoring Program of the California Department of Health and the March of Dimes, NEB has participated in the establishment and is sharing in the utilization of a population-based registry of children with cerebral palsy in four counties of the San Francisco Bay Area for births in 1983-1985. Cases were ascertained through client records of the California Childrens' Services and the Regional Centers for the Developmentally Disabled. Cases meeting CP registry criteria have received a standardized examination by a single-study pediatrician, including videotaping of all children, photographs of teeth and hands and systematic scrutiny and measurement for dysmorphologic features. All children meeting registry criteria have been examined. In this birth cohort of approximately 156,000 children, 192 cases have been identified, excluding those with abnormalities related to events after the first month of life. Analysis using the examinations, birth certificates, initial interview, and linkage with birth defects registry information are imminent. The information will permit descriptive studies of prevalence and distribution of cerebral palsy, evaluation of markers of maldevelopment, and exploration of risk factors, medical and environmental. Ecologic studies will compare rates of CP among births in Santa Clara County census tracts containing EPA superfund waste disposal sites to rates in the county as a whole and to rates in the remainder of the Bay area. Trends in incidence and time-space clustering will be sought and hypotheses formulated for testing in case-control studies.